Lapping machine



March 15, 1938. R. s. DRUMMOND.

LAPPING MACHINE Filed Aug. 7, 1935 4 Sheets-Sheet l "JVENTOR ROBERT S.DRUMMOND March 15, 1938. R. s'. :nwuwnficru:v

LAPP ING MACHINE Filed Aug. 7, 1935 4 Sheets-Sheet 2 INVENTOR ROBERT S.DRUMMOND BY 1 ll PW ATTORNEY 5 R, s. DRuMMoN March 15, 1938.

APPING MACHINE Filed Aug. '7, 1935 4 Sheets-Sheet 4 I'll EQEQ

GEAR FACE WlDTH LBS.

RESSURE :NVEN ROBERT DRUMMOND S Y E N R O T T A Patented Mar. 15, 1938 UNITED STATES PATENT OFFICE I LAPPING MACHINE Robert s. Drummond, Detroit, Mich.

Application August *7, 1935, Serial No. 35,11d

I 8 Claims.

The invention relates to the artof finishing gears and is an improvement in the invention disclosed in my prior Patent No. 1,989,651 patented January 29, 1935.,

tain a crowning effect during the finishing of the gears whereby the ends of the teeth are slightly rounded. When gears finished in this 10 'manner are run together, there is avoided the gears may be very slightly out of line in the mounting of the case.

My invention .may be applied to machines adapted for lapping, burnishing or cutting of gears and is particularly adapted for improving the finishing of gears by the method shown in my prior patent above mentioned. My invention 7 may be embodied in an attachment which can be added to the machine shown in my prior patent, or it may be made as an integral part of a machine for finishing gears."

My invention is especially adapted for use in lappinggears by means of arotary lapping tool in theform of a gear, the axis of the tool being crossed with respect to the axis of the gear being finished, preferablyat an angle of less than 30. The invention is also efiective when'the rotary finishing tool is of a form to produce burnishing- ,or of a form to produce cutting or shaving of the gear teeth.

In the drawings I Figure 1 is a perspective view of a gear finishing machine-embodying my invention with cer- The principal object of the invention is to ob-,

harsh edge bearing which in the case of ordinary tain portions of the oil pump in the power tail stock diagrammatically. shown in dotted lines;

Figure 2 is a vertical section through the machine;

Figure 3 is a sectional view illustrating a portion of the drive mechanism taken substantially 40 on the line 3'3 of Figure 2;

' Figure 4 is a horizontal sectional view taken on the line 4-4 of Figure 2;

Figure 5 is a detail view of a portion of Figure I 1 with parts broken away;

Figure 6 is a diagrammatic sectional view through the power tail stock showing the oil pump and valves;

Figure 7 is a top plan view of the mechanism for varying the oil pressure in order to obtain 30 the crowning efiect;

Figure 8 is a diagrammatic view showing the relationship between the gear and the finishing tool during the finishing operation;

Figure 9 is an enlarged diagrammatic view of 5 the gear teeth of a helical gear after the crowning effect has been produced, the rounding of the teeth being somewhat'exaggerated;

4 Figure 10 is a diagram illustrating the change in oil pressure during the reciprocation of the gear with respect to the finishing tool.

The drawings illustrate a machine which in general construction is substantially the same as that disclosed in Figures 6 to 11 of Patent No. 1,989,651, but modified therefrom to obtain the invention. It is also substantially the same as one of 'the machines shown in my co-pending application, Serial No. 3,663, filed January 26, 1935. The machine is provided with a hollow base 60 which at a convenient height is provided with a table 6|. At the rear of the table are segmental ways 62 on which is mounted a vertical column 63. At the front of the table 6| provision is made for carrying the arbor 64 on which the finishing tool 65 is mounted. This consists of a head stock 66 and tail stock 61, the latter being adjustable in the ways 68 on the table 6| These are so located that the horizontal axis of the arbor 64 intersects the vertical axis "about which the column 63 is angularly adjustable on the ways 62. For adjusting the finishing tool axially there is provided the square shank 69 which carries at its opposite end the pinion 10 (see Figure 5); The pinion 10 meshes with the rack H on the sleeve 12 which in turn has a collar 13 abutting the finishing tool 65. Thus upon rotation of the square shank 69 with a suitable handle, the finishing tool 65 may be axially adjusted in the hearings on the head stock 66 and tail stock 61.

The column. is provided with vertical ways 14' for mounting the crosshead 15. The crosshead is in turn provided with horizontal ways 16 on which is horizontally adjustable a carriage 11. This carriage has depending therefrom arms 18 and I9 in which are mounted bearings for the arbor 80 for the gear 8| to be finished. For. vertically adjusting the arbor 80, the following mechanism is used. The column 63 is provided at the top thereof with a frame 82 in which a handwheel 83 is journaled. The handwheel carries a worm 84 engaging a worm wheel 85 which in turn is mounted on the adjustment screw 86.

This screw threadedly engages a nut 81 on the crosshead I5 while it is provided with a suitable thrust collar, 88 to prevent axial movement thereof. The screw also carries at its upper end the index wheel 89 for indicating the vertical adjustmentof the crosshead.

The arbor 64 is driven by suitable means such crowning effect in accordance with the present, 10

as the pulley 90 which is connected by a belt 9I to a pulley 92 on a shaft 93 arranged in the bottom of the hollow base 60. The shaft 93 has a gear 94 engaging worm 95 on a shaft 96 driven by an electric motor 91. The speed of rotation of the arbor 64 for the finishing tool may be suitably regulated by providing the proper ratio of the gears in the driving mechanism. Provision is also made for automatically reciprocating the carriage 11, this comprising a rack 98 on the carriage 11 engaging a gear wheel 99 splined upon a vertical shaft I00 which is oscillated by a rock arm IOI connected to a link I02 engaging an adjustable throw crank I03 on a shaft I04. The shaft I04 is driven through the medium of a reduction worm gearing I05 from the shaft 93. Thus the rotation of the shaft 93 rotates the gear finishing tool 65 and at the same time reciprocates the gear to be finished in the direction of the axis of the latter. The amplitude of movement is determined by'the throw of the adjustable crank I03 which may be set according to the width of the gear which is being finished. The rate of axial feed of the gear may be determined by the proper gear ratio.

In the finishing of gears according to the present invention, the pressure between the teeth of the finishing tool and the gear to be finished is developed by retarding the rotation of the gear, and for this purpose I provide a suitable mechanism which may be referred to generally as a power tail stock I06. This is mounted on horizontal ways I20 on the column 63 to permit horizontal adjustment. Within the power tail stock is a gear pump I01 which is driven from the shaft 80 through the medium of intermeshing gear wheels I08 and I09. The gear I08 is mounted on a shaft I2I which has at its opposite end loosely mounted thereon the driven oil pump gear I22. The gear I09 is keyed to a parallel shaft I23 to which is keyed the driving oil pump gear I24. The oil or other fluid propelled by the pump is supplied by a reservoir H0 and is discharged against the resistance of a spring-closed valve I25. Figure 6 shows .diagrammatically the path of flow of the fluid from the reservoir to the gear pump and back to the reservoir again, and for convenience the various connections are shown in substantially the same plane, although it is to be understood that in the actual construction' of the machine the conduits and the relief valves may be located in whatever relationship is found most suitable from a manufacturing standpoint. As shown inthe drawings, the pump gears I24 and I22 are within ablock I26 having intersecting cylindrical bores I21 and I28 forming the pump casing. .Conduits I29 and I30 lead from opposite sides of thecasing and communicate respectively with vertical passageways I3I and I32 leading to the top of the block I26. There are also the branch passageways I33 and I34 communicating with the enlarged bores I35 and I36 at the top of the block. The upper block I31 has vertical passageways I38 leading between the bore I35 and the reservoir H0 and there is a corresponding vertical passageway I39 leading from the bore I36 to the reservoir. Spring-closed relief val' ws I40 and I are arranged in the bores I35 and I36 to seat against the lower face of the upper block I31. There are similar enlarged bores I42 and I43 in alignment with passageways I 3| and I32 and having therein the spring-closed relief valves I44 and I45 seating against the upper face of the look block I26. The bores. I42 and I43 communicate with a horizontal passageway I46 which in turn communicates with a vertical passageway M1 in which the relief valve I25 is located. A tubular conduit I48 extends through the reservoir and projects above the same. duit is an adjustable sleeve I49 carrying within the same a push rod I50. A head I5I at the lower end of the rod I50 bears against a coil spring I52 which in turn bears against the ball valve I25. The spring tension of the valve may therefore be adjusted by vertical movement of the push rod I50 and an initial tension may be obtained by the adjusting sleeve. I49 which at its lower end abuts the head I5I.

With the construction of oil pump described, the resistance to rotation will be obtained when the pump is rotated in either direction. Thus assuming that gear I24 is rotating clockwise in the figure, the oil from the reservoir Il0 will' flow downwardly through passage I39 through relief valve I4I, passage I34, passage I32, passage I30 to the gear casing. It will then travel back to the reservoir through passageways I29 and I3 I relief valve I42, passage I46, passage I41'to the relief valve I25 and thence outwardly through the port I53 in the tubular conduit I48. Similarly, if the pump gear I24 is rotating in a counter-clockwise direction, the oil will flow downwardly through passage I38, relief valve I40, passages I33, I3I, and I29 to the gear pump casing and will flow back to the reservoir through passages I30, I32,'relief valve I45, passages I46 and I41 to the ball valve I25 and thence outwardly through port I53. It will be obvious therefore that in either direction of rotation the resistance to rotation of the gear to be finished will be dependent upon the spring tension on the relief ball valve I25.

In accordance with my invention, I make provision to vary the spring tension on the relief valve I25 in accordance with the position of reciprocation of the gear being finished. For this purpose I provide on the carriage 11 a pair of brackets I54 and I55 in which is journaled a rock shaft I56. An arm I58 adjustably secured to the rock shaft by a screw I59 extends over the upper end of the push rod I50 and is provided with an adjusting screw I60 projecting through the same and contacting with the upper head I6I of the push rod. A torsional spring I51 having its ends anchored in the rock shaft and bracket I54 respectively actuates the rock shaft to remove the lever I58 upward away from the push rod. A second rocker arm I62 on the. rock shaft I56 has a roller I63 thereon adapted to contact with the edge I64 of a plate I65 which in turn is mounted on the crosshead 15 of the machine. Two cam plates I66 and I61 are secured to the plate I65 on opposite sides of the roller I63 and have cam faces I68 and I69 respectively positioned to contact with said roller during the reciprocation thereof, the cam plates having angling slots I10 for receiving the locating screws I1I in order to permit adjustment of the cam plates. This permits of varying the pressure as desired at each end of the stroke and permits the proper adjustment to be made for different gears requiring a different length of stroke.

In the operation of the machine as described, the driving motor 91 is energized, thereby rotating the gear finishing tool 65 which in turn causes the gear 8I to be rotated due to the intermeshing action of the teeth. A reciprocating feed movement is imparted in the direction of the axis of the gear by means of the automatic mechanism including the pinion 99 and rack 98 Within the tubular conwhich cause reciprocation of the carriage Ill and the gear 8|. This movement is of suflicient amplitude to spread the finishing action over the entire face width of the gear. The finishing tool is' provided with a tooth thickness that is less than the interdental spaces in the gear prior to lapping which enables the original setting of the machine with the gear and finishing tool in full mesh, that is, with their axes spaced apart the exact distance for normal operation. The driving motor 91 is first operated in one direc-- tion to cause a finishing action on the tooth A only slightly wider than the gear 8|.

faces on one side thereof, and then by reversing the motor the opposite faces of the teeth are correspondingly subjected to a finishing action. The reversal of rotation may be accomplished manually, or if desired suitable timing mechanism can be used for automatically reversing the machine after a predetermined amount of finishing action in one direction.

During the axial reciprocation of the gear M, the roller IE3 is also reciprocated and bears against the edge I64 until near the end of the stroke 'when it rides up on one or the other of the cam faces I68 and I69. This causes a rocking movement of the rock shaft I56 against the action of the torsional spring I57! and the arm I58 presses downwardly on the push rod I50, thereby increasing the spring tension on the ball valve I25. Therefore the oil pressure is built-up to a higher degree which causes an increased retardation of the power tail stock and .an increased pressure between the ends of the teeth of the gear being finished and the teeth of the finishing tool. This is diagrammatically illustrated in Figure 10 which is a pressure chart showing the change in oil pressure over the face width of the gear. Thus if the relief valve is set to normally operate under 20 pounds pressure when the roller is contacting with the edge I64, the pressure will rapidly build-up when lapping the ends of the gear to pounds due to the efiect of the cam faces I68 and I69 on the position of the roller. It is to be understood that the pressure chart is illustrative only, and the presdesirable for any particular gear finishing oper- Figure ,8 diagrammatically illustrates the correct setting for crowning gears in accordance with my invention. In this case the lap 65 is The reciprocating stroke is sufficient so that at each end of the stroke only the ends of the gear teeth are in contact with the lapand it is at the ends of the stroke where the obtain tl'fe increased lapping eifect. Asv an illustration, if the gear has a face width of' 11 3' inches, the lap may have a face width of 1% inches and the stroke may be 1% inches. This, however, may be suitably varied and still obtain a beneficial effect. It should be remembered that the-gear and lap are arranged with crossed axes so that the contact between the teeth of the gear and lap varies from the center position toward the positions at the ends of the stroke. The angle of conta'ctis different at. the ends of the stroke than at the center of the crossed axes. Another factor in the production of pressure is built-up tobecomes relatively larger with respect to the lapping in the middle of the gear. This in itself will cause excessive lapping at the ends of the stroke and tends to chamfe'r or round the ends of the teeth. N a

Figure 9 is a diagrammatic view of the teeth of a helical gear which have been crowned in accordance with my invention. The chordal thickness in the middle of the gear is for example. thousandths of an inch, while the chordal thickness at the ends is 124 thousandths of an inch. This is merely an illustration however, and by means of my invention the ends of the teeth may be tapered off in any desired amount even to as much'as 2 thousandths of an inch if desired. A gear, finished in this manner is recognized as desirable due to the fact that in use it eliminates a very undesirable whine sound caused byniis-alignment of the shafts or edge bearing between the gears.

In the previous description of the operation of the machine, I have referred more particularly to lapping and as is well understood in the art tool of a relatively soft material such as cast iron, while burnishing is obtained with a finishing tool of harder material. Cutting 0r shaving is obtained by the use of a modified form of finishing tool as described in my co-pending application, Serial No. 3,662, filed January 26, 1935. Where the term rotary finishing tool is used in the specification and claims, it is meant toinclude within its meaning constructions useful for lapping, burnishing or cutting.

In finishing gears in accordance with my invention, the gear finishing tool and the gear to be finished have conjugate mating teethand the angle between the axes'is preferably maintained less than 25 to 30 and usually between 3 and 20. If the gear to be fini shed is a straight spur gear, the finishing tool will be a helical gear having a helical angle within the above limits. On

the other hand, if the gear to be finished is helica-l, the finishing tool may be in the form either of a-straight spur gear or of a helical gear, but in each case the difference in helical angle should be such that when in proper mesh the angular difference between the axes is within the limits. previously mentioned.

What I claim as my invention is:

1,. A gear finishing machine comprising two arbors having their axes crossed at-an angle less than 30, one of said arbors being adapted to mount a gear member to be finished, a rotary finishing tool in the form of a gear member mounted on the other of said arbors to mesh with said gear to be finished, means for driving one of said arbors whereby the, other of said arbors is driven by the intermeshing action of said gear members; means for resisting the rotation of said other arbor, means for feeding one of said members relative to the other in the direction of the axis of the gear to be finished and means automatically operated in timed relation to said feeding movement for varying the resistance to rotation of said other arbor during the feeding movement.-

2. A gear finishing machine comprising two arbors having their axes crossed at an angle less other of said arbors is driven by-the intermeshing action of said' teeth, an oil pump driven by said other arbor, a relief valve for placing a predetermined resistance on said oil pump, means for feeding one of said members relative to the other in the direction of the axis of the gear to be finished and means for varying said relief Valve during said feeding movement to vary the pressure between the teeth of said members.

3. A gear finishing machine comprising two arbors having their axes crossed at an angle less than 30, one of said arbors being adapted to mount a gear member to be finished, a rotary finishing tool member mounted on the other of said arbors to mesh with said gear to be finished, means for drivingone of said arbors whereby the other of said arbors is driven by the intermeshing action of said teeth, an oil pump driven by said other arbor, a relief valve for placing a predetermined resistance on said oil pump, means for feeding one of said members relative to the other in the direction of the axis of the gear to be finished, a rock shaft operatively connected. to said relief valve to vary the pressure on said oil pump and cam means operatively associated with said rock shaft to rock the same during said feeding movement.

4. A gear finishing machine comprising an arbor having a rotary finishing tool thereon,

-means for rotating said arbor, a second arbor having an axis crossed at an angle less than 30 with axis of said first arbor and adapted to mount a gear to be finished in mesh with said rotary finishing tool, a gear pump driven by said second shaft, a relief valve for said gear pump, a movable rod for varying the pressure on said relief valve, a reciprocable carriage for mounting said second arbor, a rock shaft on said carriage, an arm on said rock shaft operatively associated with said rod, a roclier arm on said rock shaft and a stationary cam arranged in the path ofsaid rocker arm to move the same during the reciprocation of said carriage.

5. A gear finishing v machine comprising a frame, a pair of shafts in said frame, means for angularly adjusting one of said shafts on said frame to cause the axes of said. shafts to be crossed, one of said shafts being adapted to mount a work gear membr to be finished, a rotary finishing tool member mounted on the other of said shafts and having gear teeth adapted to mesh with said work gear when said axes are crossed, means for driving one of said members whereby the other of said members is driven by the intermeshing action of said gears, meansfor feeding one of said members relative to the other in a direction to spread the finishing action across the face of said work gear, means for regulating the pressure contact between the teeth.

of said'members, and means for actuating said pressure-regulating'means in predetermined portions of said feeding-movement.

6. A gear finishing machine comprising a frame, a pair of shafts in said frame, means for angularly adjusting one of said shafts on said frame to cause the axes of said shafts to be crossed, one of ,said shafts being adapted to mount a work gear member to be finished, a rotary finishing tool member mounted on the other of said shafts and having gear teeth adapted to mesh with said work gear when said axes are crossed, means for'driving one of said members whereby the other of said members is driven by the intermeshing action of said gears, means for feeding one of said members relative to the other in a direction to spread the finishing action across the face of said work gear, means for resisting'the. rotation of said driven member, means for regulating the amount of said resistance to rotation, and means automatically responsive to travel of said fed member for actuating said regulating means in predetermined portions of said feeding movement to vary the pressure contact between said members in different portions of the face width of said work gear.

'7. A gear finishing machine comprising a frame, a pair of shafts in said frame, means for angularly adjusting one of said shafts on said frame to cause the axes of said shafts to be crossed, one of said shafts being adapted to mount a Work gear member to be finished, a rotary finishing tcol member mounted on the other of said shafts and having gear teeth adapted to mesh with said work gear when said axes are crossed, means for driving one of said members whereby the other of said members is driven byw the intermeshing action of said gears, means for feeding one of said members relative to the other in a direction to spread the finishing action across the face of said work gear, means for resisting the rotation of said driven member, means for regulating the amount of said resistance to rotation,

and cam means operably connected to said feedframe to cause the axes of said shafts to be.

crossed, one of said shafts being adapted to mount a work gear member to. be finished, a rotary finishing tool member mounted on the other of said shafts and having gear teeth adapted to mesh with said work gear when said axes are crossed, means for driving one of said members whereby the other of said members is driven by the intermeshing action of said gears, means for feeding one of said members relative to the other in a direction to spread the finishing action across the face of said Work gear, means for resisting the rotation of said driven member, means for regulating the amount of said resistance to rotation, and cam means operably connected to said regulating means and operably connected to said" feeding means to increase the pressure con tact between said members at the ends of said work gear.

ROBERT S. DR JMMOND. 

